To minimize airport closures caused by volcanic ash, aviation authorities should make more use of methods that are now available for measuring airborne particles.

Optical particle-counter (OPC) instruments were used to measure dust pollution during Iceland's Grímsvötn volcano eruption in May this year, after a trial last year in Eyjafjallajökull's ash plume. The data were used by Isavia, the country's air-navigation services provider, to help in decision-making.

OPC instruments measure airborne concentrations of three different size classes of particulate matter components and total suspended particles, every 6 seconds. The instruments were mounted on a light, slow-flying, piston-engine aircraft after calibration in wind-tunnel experiments with volcanic ash.

As Grímsvötn erupted, OPC results were quickly dispatched to the local meteorological office and to Isavia. This helped to keep Keflavik International Airport open for longer than expected, resulting in large savings for the airline companies.

Other European aviation authorities are considering similar operations. Also, universities in Iceland and Japan are considering using OPC measurements to improve modelling of ash-cloud events.